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therefore no surprise that vast efforts were made to discover new nearby associations in recent years. Today, seven nearby associations, open clusters, or so-called ”groups” are known, that are closer than 100 pc from the Sun with ages of ∼ 10 Myr, or less. We have conducted adaptive optics surveys of several of these associations in the past 5 years, using the ADONIS, PUEO and NAOS adaptive optics systems. Figure 6.14: K-band coronagraphic image of AB Pic A and b obtained on 17 March 2003. The diameter of the occulting mask is 1.4”. In the course of this on-going deep imaging survey of young, nearby southern associations (Chauvin et al. 2003), we used the ESO VLT telescope and its adaptive optics near-infrared instrument NACO to image the close vicinity of the source 2MASSWJ 1207334-393254 (hereafter 2M1207). This brown dwarf 2M1207 was identified by Gizis (2002, ApJ, 575, 484) as a member of the young (8 Myr) TW Hydrae Association (TWA), a result corroborated later by measurements at optical, infrared, and X-ray wavelengths. In the close circumstellar environment of 2M1207 A, we discovered a faint planetary mass companion candidate in April 2004 (Chauvin et al. 2004), at ∼780 mas (55 AU). See the discovery image on the cover page of the current (FOST) chapter. Subsequent observations of 2M1207 A and b, obtained in August 2004 by Schneider et al. (2004, A&AS, 205, 1114) using the Hubble Space Telescope (HST) and on February and March 2005 with NACO by our team, clearly demonstrate that the two objects are comoving (Fig. 6.13). They enable us to reasonably confirm the status of a planetary mass companion to the brown dwarf 2M1207 A. Photometry and spectroscopy are consistent with a spectral type L5-L9.5 for the companion. Based on H, K and L’ photometry and evolutionary models, for an age of 8 +4 −3 Myr, we found 2M1207b to lie within the planetary regime, i.e., a mass of M = 5 ± 2 MJup and an effective temperature of Teff = 1250 ± 200K. As part of the same deep imaging survey of young nearby associations, we also obtained a direct image (Fig. 6.14) of a 13—14 MJup companion, assuming an age of ∼30 Myr, at 250 AU of the star AB Pic, a member of the large Tucana-Horologium association (Chauvin et al. 2005). These detections provide the first images of planetary mass companions in systems other than our own. It is very unlikely that these giant planets formed within a circumstellar disk, but more probably via one of two formation mechanisms proposed for brown dwarfs. These discoveries offer proofs that such mechanisms can form bodies down to the planetary masses and open new perspectives for our understanding of chemical and physical properties of planetary mass objects as well as their formtion mechanisms. 100
Chapter 7 Future Research Directions 7.1 Research Plans Over the last few years, since the creation of FOST in 2003, we have progressively refocussed our activities by including the unifying long-term goal of ”planet formation” to our present goal of understanding ”star formation”. Recall that the acronym FOST stands for ”Star and Planet Formation” in its contracted form. Because such a re-orientation takes time and must be smooth to maintain a good coherence within a larger team, not everyone in FOST works directly on ”planet formation” today. We are convinced this is the right way because we foresee that our broad range of expertise will lead to innovative breakthroughs in the long run, breakthroughs that would otherwise have been missed. Indeed, because of the richness of the scientific background in FOST, we are considering the problem from a number of independent and interesting directions: be it from the direct search for planets around main sequence stars and in younger star forming regions, be it the study of proto-planetary disks where planets are thought to form, or be it the impact of mass-loss on the disk structure, possibly changing the conditions for planet formation and migration, for example. This shift in perspective for FOST is rather new. As a consequence, our work should largely keep going in the current directions for the next few years, i.e., largely into the 2007-2010 period we are considering here. Therefore, a large fraction of our forecasted activities has been described in the previous chapter. It is nevertheless useful to recall a few directions we are engaged in and to raise a few questions that will, undoubtedly, drive our research in the longer term. In the field of Star Formation We plan to take advantage of JETSET (starting fall 2005) to make advances in the 2D and 3D numerical simulations of the magnetically mediated star-disk interaction zone (in relation with SHERPAS). The goal is to confront realistic models with our observations. On the observational side, our involvement in programmes using 2 powerful spectropolarimeters, ESPADONS at CFHT and NARVAL at TBL (soon), should allow us to obtain the first, and long awaited for, maps of the magnetic field in this zone. Today this field is assumed dipolar, but just how close to reality is this hypothesis? The use of X-rays to probe that zone is original and we will benefit also from the rare expertise we have in this field. Clearly, the scientific exploitation of AMBER, NACO, and WIRCAM is also at the center of our activities. The expected returns from these new instruments has been described before, but WIRCAM should allow us to identify planet-mass objects in nearby star forming regions and estimate the shape of the IMF down to a few Jupiter masses only, a key piece of information to constrain the star formation mechanisms. NAOS and AMBER will be extensively used to map disk, from their inner parts (AMBER) to signatures of large scale asymmetries (NACO), possibly tracing planets. The interpretation of these observations will require continued efforts to improve our disk models and radiative transfer tools. The need for dynamical models is expected to increase with time, together with the quality of data available from these instruments. A long term target for these studies is the preparation for Herschel and ALMA that will provide the necessary 101
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LABORATOIRE D’ASTROPHYSIQUE DE GR
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III Team ASTROMOL 41 2 Presentation
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8.1.3 Graduate Students . . . . . .
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VI Team SHERPA 145 15 Results 147 1
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Part I Foreword: Presentation of th
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Part II Executive Summary A 18th ce
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of CNRS for technicians and enginee
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Figure 1.3: New LAOG organigram (20
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heart attack. Manuel went back to t
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Figure 1.6: PhD student repartition
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1.5 From dreams to reality: Human r
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and accretion disks with heavy nume
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emphasis on the chemistry of planet
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Part III TEAM ASTROMOL Sub-arcsecon
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• we develop quantum and classica
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Table shows not only the volume of
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• Herschel-HIFI: Astromol is invo
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15.4 Transport phenomena in accreti
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states, combining a still powerful
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Excitation of turbulence by Cosmic
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Table 15.2: Former PhD students of
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Chapter 16 Perspectives The distinc
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Ray background. The second project
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Among the various areas of expertis
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-responsable du groupe ”logiciel
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